[fangz (OP)]

I've been trying to understand for a while something that i know must be really simple about quantum entanglement....
Because I think I am misunderstanding maybe what people are stating when they talk about it, but I haven't seen the 'misunderstanding' addressed in terms that I understand.  But it definitely is something very simple that I'm not making a connection on
Here is an example video...

The video is very simple but it's good for that exactly that reason, to use as an example.  And most explanations of quantum entanglement for the layperson all basically say the same and always don't explain the same little bit that throws me off...

Basically the video explains how we can have two particles and then create some event which will always result in one spinning one way and the other spinning the opposite way.
So we create this event and then keep one where it is and let the other one go off 5 million light years away.   

And then we check to see which way our particle is spinning and see it is going clockwise.

and here's the part where I'm never sure if they actually mean this....

becuz they will always go on to say that then, instantaneously and faster than the speed of light the information is transmitted to the other one that it can only be spinning counter clockwise.  and then this brings up a conflict with Einstein and how nothing can go faster than light and other things that I'm not even worried about understanding yet because I'm stuck back there with what just happened.

Because I understand it has something to do with us only being able to calculate a probability of which way the particle is spinning, until we check.  But are they really trying to say that one particle is sending the other's state as a piece of information?  And that the conflict is only in wondering how this could go faster than the speed of light?  I mean that has to be a 'cute' way of saying something else right?  I can't tell becuz no one explains the obvious problem that I think everyone is going to have at this step, but at the same time, they seem to be taking pains to explain everything as simply as possible.  Except for this huge gaping hole in the gameplan.

Why isn't it assumed that the direction each particle was spinning was determined at the time of the event?  then the second particle would take it's information on it's own state with it so there'd be no communication between particles?  I'm guessing this is what the probability thing explains but doesn't it seem more likely that we can only measure it as a probability becuz of some limitation in how we currently know how to measure things?

or are some scientists really saying that it's only once we check something that forces it into place somehow?  Becuz how would these particles 'know' if we checked or not?  it brings up too many questions that I must be misunderstanding something.

becuz even if a particle 'knew' that it was checked, how did it 'know' that we checked it correctly?
what if we mischecked it and thought it was counterclockwise, would it 'tell' it's partner particle to go along with our misperception?
what if one of us checked it and saw it was spinning clockwise but another of us read it wrong and said it was going counterclockwise?
i mean I know that no one is saying that particles know things or send each other information, but it's the only way to talk about it I guess and I'm wondering what real scientists actually think is going on when they say that we 'check' something or that particles 'send' information to each other.

and then also, in these examples, it's always assumed that nothing has happened to the particle over this whole 5 million light years it went. 
how do we know some other scientist didn't use the same particle to create a similar event but paired it up with a new partner particle.  so they do their event and then does the particle listen to it's first partner or it's second now?
wouldn't there possibly be a billion such events that could change the direction of the particle every time, so that by the time we checked the particle we kept here, how much of a relationship would it still have to the other particle?

once a particle has been checked once as going one way, if we check again later is it still going the same way every time?
what if someone else checks it secretly before i do? then i'm not really checking it at all, becuz it's already been determined which way it's spinning, right?
what if at the moment of this event, it got checked which way it was spinning but it was by tiny little scientists who never talk to us about anything?
you see what i'm getting at?  even if u say that we don't know which way it's spinning until we check, what does that mean at all?
i'm not being facetious too, but there's no way to talk about it without seeming like u are, it just seems so ridiculous.

So is all this just an example of scientists dumbing down quantum entanglement for people like me?
Why don't they explain the obvious question everyone is going to have back there?
if seems like there's more problems the further in you get, becuz at some point you do start hitting issues of what's so special human consciousness?
why do we assume that we're the 'checker's of particles?  just saying that nothing really exists until we make it up in your heads by 'checking' seems like all these scientists really wasted their time learning anything, you know?  i mean, not for practical purposes, but if we don't know anything about the world until we 'check' then how do we know we even checked anything?

thanks, i hope I was able to explain why this is so baffling to me, I'm actually not so much right now trying to argue at all against quantum physics but more trying to figure out if these scientists are really saying what it seems like they are.  Which, really just seems stupid to me.

[yor_on]

A entanglement  can be done with a beamsplitter, separating one photon into two, down converting the original photons energy '1' to two photons of '.5', in where the subsequent photons now will have opposite polarizations (spin) and so becomes 'entangled'.

The weird thing about entanglements are that they are supposed to instantly set their states, as soon as you measure one. Either you can assume some hidden parameter creating the 'spins', at their creation? Or you can assume a entanglement to ignore distance and light speed.

Also, there is no way for you to know what the spin will be on the particle you measure on, before the measurement. It has a 50% chance to be 'up' or 'down'. But no matter what polarization/spin it is found to be, the other particle will 'know' and set the opposite.
=

And no, you can't really define what happens to them outside a 'laboratory', it's like with everything else. As soon as you open that door

[fangz (OP)]

thanks for replying.  what you're saying confuses me for the same reason a little tho...

becuz there's no way for me to know what the measurement of anything is before i measure it, no?  Or I guess, maybe this is where part of my confusion might lie, but what do u mean by measuring?  maybe i am being too loose in what that word covers.  to me, it would be strange to think it should be possible to know any quality of a particular thing before I measured it.  does that make sense?

but do you mean, for example, if i meet a person and i see they are taller than i am, and i know that i am 5' 11", then without measuring, i know they are taller than 5' 11"?  i guess maybe this would translate to an equation with math people.  so do u mean that sometimes, even tho we can't measure things, we can figure out their qualities from equations we have?
but that with polarization of particles, there's no equation that could possibly help us?  so we have no choice but to actually go measure these things?  i guess that kind of makes sense to me if that's what u mean. 

but deeper down that part, when u are saying that after we know what one particle is, it sets the other one....

why isn't it simply that splitting a photon will result in two photons of opposite polarizations?  end of story?  where does entanglement come in?  it seems more like, we just don't know the physical principles involved at this level and maybe they are beyond the capability of our understanding.  but that doesn't mean that an event doesn't have an effect without us checking it first right?

i guess i have a hard time with the idea that scientists make what seems to me like an absolutely crazy leap to this idea that one photon is communicating with the other one instantaneously to make it aware of some essential quality about itself.  and it comes down to me being stuck on a belief that things actually happen whether i am looking or not. 

is this just a fundamental split that some people have?  i mean, not like me, but that are actually scientists?  i know Einstein had a problem with this becuz videos explain 'spooky distance' but was his problems with it really the same as what i'm talking about?  it sounds like that's not the case, that he understood what they were talking more than i do.

i think part of it is that i have a problem with the definition of what it means for me to 'look' at something else.  and why it's so important that i be the one to do it.  becuz if they're gonna say that the moment i 'look' is some kind of event that in turn triggers this photon to shoot information faster than the speed of light to another photon, then they're actually saying that some chain of events happened at a particular time.  but who's the judge of whether i 'looked' at something or not and when the exact moment was that the 'look' happened at?

i think that's what strikes me as the craziest thing.  what if i didn't know anything about polarity and u told me to go check what our photon was.  and i came back and said, well...it's "pretty purple.  and it looks like it's gaining weight" polarity.  and u said no no no.
there's two polarities, don't make up a third one now....
so how would that make this photon be measured in any way, seeing as how i just made up a third polarity?  i just don't know what i'm talking about, so what is the measurement of that?

i'm starting to think that maybe the problem with quantum physics all comes down to semantics.  it's like a theoretical way of expressing things but then it's imposed upon the real world which is quite different and not understood by us and isn't influenced at all by what we understand or don't.

so is it really just semantics that i'm talking about with this?

for example, i thought this one thing a few years ago....No One Ever Really Dies.  and this meant that in the sense of pure truth, i will never be dead.  and i have to presume there's no afterlife to come to this conclusion, but if someone jumped in my window right now and shot me in the head a bunch of times, i'd start dying and maybe i'd realize i was dying....and then in the next fraction of a second, be dying even more and so on and so on, but i'd never look at myself and say 'i'm dead now'.
becuz, to me, just the fact that i'm conscious of anything means that i'm not dead and never gonna be dead.
but when someone shoots me in the head, none of this will matter, regardless of the truth's i can take from it.

so do u think it might just be a matter of semantics like this?

[yor_on]

I would say it's the other way around

You have experiments telling you something, you then translate that into mathematics describing it. If you find the right equations you, by manipulating them, might define more relations and test them with a new experiment. And when you do it you might have to invent new words, or meanings for a old word, to describe what the mathematics and the experiment tells you. So the semantics comes after to me.

[Pmb]

becuz they will always go on to say that then, instantaneously and faster than the speed of light the information is transmitted to the other one that it can only be spinning counter clockwise.

Whoever said that made a mistake since in measuring the spin of one of the particles it only places the system into one of the two possible eigenstates. But in doing so no information is being transmitted.

[JP]

becuz they will always go on to say that then, instantaneously and faster than the speed of light the information is transmitted to the other one that it can only be spinning counter clockwise.

Whoever said that made a mistake since in measuring the spin of one of the particles it only places the system into one of the two possible eigenstates. But in doing so no information is being transmitted.

Indeed.  It's as if you have two sets of two coins. One set is arranged heads + heads, and the other is arranged tails + tails.  You send one coin from each pair to the other side of the world and keep one with you.  You then randomly pick one of the coins and look at it.  You instantly know what it's partner coin is without sending information.

The weird thing about quantum mechanics is that a pair of quantum coins can be in both states at once, i.e.  when you look at it, you have a 50% chance of seeing a heads + heads pair and a 50% chance of a tails + tails pair. 

[fangz (OP)]

oh wait!!!
you mean every time?

cuz then that answers my question, please say that's what u mean?
that every time i check the coin that i kept, there's a 50% chance of it being one or the other....

[dlorde]

... please say that's what u mean?
that every time i check the coin that i kept, there's a 50% chance of it being one or the other....

The coins are just an analogy. With the particles, checking (measuring their spin) disentangles them, so it only works once per pair.

[fangz (OP)]

... please say that's what u mean?
that every time i check the coin that i kept, there's a 50% chance of it being one or the other....

The coins are just an analogy. With the particles, checking (measuring their spin) disentangles them, so it only works once per pair.

does measuring the spin change the particles in some way?

i don't understand how a particle can 'know' that it's been measured.

[fangz (OP)]

ok, here's another way of asking the question about what i don't understand about this.....
(and thanx a lot for all you're answers so far)  i'm positive this is something that's really, really simple about how i'm not grasping this, and thank u so far for trying to help me....

here's another way of phrasing the problem i'm having....

I have a wife.  one day she tells me she has two older twin sisters and they are coming over right now for lunch with us.  there's a knock at the door right then and my wife's sisters walk in.  one is blonde and the other has dyed her hair red...

i whisper to my wife  "what are their names?"

my wife says "Ariel and Leira"

i say "which one is Ariel and which one is Leira?  Is Ariel the blonde or the redhead?"

my wife whispers back "i don't know.  see, my family is weird.  there's always been a rule that if there's twin girls born, one's named Ariel and the other's named Leira, but it's random which one gets named Ariel.  but the one that's not Ariel is gonna be named Leira"

and then I say "oh.  that's a strange custom you guys have.  so which one is Ariel, the blonde or the redhead?"

and then my wife says "i told you, i don't know.  i know they are my sisters but i've never asked either of them."

i say "oh".  my wife says "just ask the blonde what her name is.  then u will know the name of the redhead, if the blonde says she's Ariel, the redhead must be Leira.
but if the blonde says she's Leira, then the redhead must be Ariel.  just ask the blonde what her name is..."

i turn to my blonde sister-in -law and i ask  "hi. nice to meet you, what's your're name?"

she says 'Ariel'.  i say 'oh, hi Ariel' and then i turn to the redhead and say 'hi Leira'.
they both smile and are happy with my wife's choice to marry me.

so that's the example, but there's two ways to interpret what just happened in it.

here's possibility 1.......this is what it seems like quantum entanglement is saying.....
my wife's sister were not named when they were born.   they were only told the rule that they were either Ariel or Leira but never told which one was which.  i was the first person ever to ask either of them this question.  so when the blonde sister decided she was going to be named Ariel, the redhead sister knew that she must be Leira.

here's possibility 2.......when they were born, their mother gave them names, it's just that my wife never cared to ask them which was which.

see what i mean?  why would we assume that their mother never gave them names?  they were named when they were born most likely, right?

[fangz (OP)]

just now i'm starting to think this must really be semantics.

it quantum entanglement just a theoretical thing?  like it's a way of abstractly dealing with probabilities?
do people who believe it's true also believe there is one reality that if i draw one card out of a deck and burn the rest of the deck, maybe in theory, it could be any card out of a standard deck, but in reality it is the one card i picked. 
like if i was shot in the head before i turned it over, it still is whatever card i picked right?  that's reality

[dlorde]

i don't understand how a particle can 'know' that it's been measured.

To measure some property of the particle, you have to interact with it in some way, e.g. bounce a photon off it. This has an effect on the particle.

[dlorde]

here's possibility 1.......this is what it seems like quantum entanglement is saying.....
my wife's sister were not named when they were born.   they were only told the rule that they were either Ariel or Leira but never told which one was which.  i was the first person ever to ask either of them this question.  so when the blonde sister decided she was going to be named Ariel, the redhead sister knew that she must be Leira.

here's possibility 2.......when they were born, their mother gave them names, it's just that my wife never cared to ask them which was which.

You're right, quantum entanglement is more like possibility 1. The particle you measure gives the appearance of randomly choosing which spin it will have at the point of measurement, and the distant particle is always found to spin the other way.

As I understand it, possibility 2 is known as the 'hidden variable' explanation because the twins each have a definite name from the start, it's just hidden until you ask. This common-sense, intuitive explanation has been shown to be false by experiments based on Bell's Theorem. Bell worked out that if possibility 2 was true, measuring a lot of particle pairs should give a certain distribution of results. Experimentally, it's been shown that you don't get this distribution of results, so, however weird it seems, possibility 1 is what really happens.

[dlorde]

it quantum entanglement just a theoretical thing?  like it's a way of abstractly dealing with probabilities?

It's real; it's being demonstrated in labs all round the world. It's now being used commercially for exchanging cryptographic keys in secure communications systems, and may soon be in commercial quantum computers.

[Bill S]

Fangz, I really like that twins analogy!

It's real;

We know it's real because it works when we use it.  However, like so many things in QM, clever experiments and successful practical applications may be our best proofs of reality.  Perhaps there is no point in asking why they work, and what the underlying reality might be. 

Personally, I see no reason why those who want only to work with QM should be expected to divert their efforts into asking what "reality" might be behind it all.  On the other hand, I think those who want to ask should be encouraged to do so.

I don't necessarily subscribe to the view that if a scientist cannot explain an idea or principle in such a way that the "ordinary person" can understand it, he/she does not understand it.  However, I do believe that those who supplement their income by writing popular science books have a duty to deliver the goods in a suitably understandable way.  Many do this very well, but a lot fall well short.

Look at that! A whole post without the "I"- word.

[yor_on]

The point with the sister here is that they both, have both names, before your asking, (also called a 'super position'). You asking one will 'force' a settlement of names (measuring). And the other sister doesn't 'need to know' what name the first sister gives, she must have (and 'know') the other name, directly at your measurement of the first according to the experiments we've done so far.

And there is no way a name can be known without measuring, and when you measure you will find a probability of it being one or the other (50/50% probability). So without measuring you have - 'both names just as  possible'-, and no one can define which one it is, after measuring one you have -  'both names set' -, without them communicating.

So you can put the sisters at different locations, Rio de Janeiro and New York, enclosed in locked rooms without communication. As soon as you 'measured' the first sister, asking her name, the other sister must 'have' the opposite, and that can be checked.
=

Never try a brew, and logic..

[dlorde]

The point with the sister here is that they both, have both names, before your asking, (also called a 'super position'). You asking one will 'force' a settlement of names (measuring). And the other sister doesn't 'need to know' what name the first sister gives, she must have (and 'know') the other name, directly at your measurement of the first according to the experiments we've done so far.

I like the way JP put it, earlier; it's as if there are two sets of twins and your measurement of one selects which pair you're dealing with.

[Bill S]

Twin sisters: "Ariel and Leira".
Mother chose both names, but didn't specify which was which.
Neither sister chooses a name.
Neither sister knows which name the other will opt for if asked.
Later, one is in London, the other in New York.
Fangz asks the one in London her name; she says "Ariel".
At exactly the same (prearranged) time, JP asks the one in NY her name.
Is it certain she will say: "Leira"?  If so, why?   

[Bill S]

I like the way JP put it, earlier; it's as if there are two sets of twins and your measurement of one selects which pair you're dealing with.

I assume you mean the example with the coins. I see the analogy, but don't see how it avoids hidden variables.

[dlorde]

I assume you mean the example with the coins. I see the analogy, but don't see how it avoids hidden variables.

It's just an analogy for how it appears to the observer, nothing to do with hidden variables.